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Can calcium ions be used as a source of entangled photons

  1. Feb 8, 2016 #1
    By heating calcium in a tantalum oven and subjecting the calcium vapor stream to blue laser, calcium atoms absorb the blue photons and emit two photons of lower energy as they decay twice.

    Once they decay from the highest excited state to an intermediate excited state, and then from the intermediate excited state to the lowest energy state.
    This double decay creates a pair of entangled photons.

    I do not afford maintaining the high temperature needed to vaporize calcium for too long.
    So instead, a concentrated water solution of a calcium salt could provide the alternative?

    Do I still get entangled photons if I use a laser to excite calcium ions in a solution in water?
     
  2. jcsd
  3. Feb 8, 2016 #2

    DrChinese

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    You might get the occasional pair if you use a properly tuned laser. You will mostly get a lot of "noise" - which is common for many setups. So you use filters and coincidence counting to produce an entangled stream. Realistically you aren't going to get much from this configuration. The method you referenced, in its best setup, is not much used anymore due to better (more efficient) methods being available. So anything less than that would not be practical.
     
  4. Feb 8, 2016 #3

    DrChinese

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    BTW, you might be interested in this article about entanglement using a beam splitter.

    http://arxiv.org/abs/1602.01907

    Note that entangled photon pairs are not produced by the beam splitter, but there is path entanglement. Since you are inquiring about different forms of entanglement, you might pick up something from their description of the setup.
     
  5. Feb 8, 2016 #4
    I know they aren't produced by the beam splitter, but as this shows http://www.unige.ch/gap/quantum/_media/publications:bib:afzelius2015a.pdf, the beamsplitter erases the information about their separate origins

    New_Bitmap_Image.png
     
  6. Feb 8, 2016 #5
    The reason I gave up using nonlinear crystals is the one you mentioned above. Most of the laser light does not get down-converted and becomes noise in the detection process. This is why I am looking for ways to entangle that involve entanglement of a large percent of the input light so that my detectors won't register noise.

    My filters do not absorb all laser light. Even red filters allow some of the blue light to pass through so I cannot use them to separate entangled photon pairs from background light
     
  7. Feb 8, 2016 #6

    DrChinese

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    Why do you think scientists use the crystals? It is because it is the best source (or at least a better source). Many other methods are being studied at this time. The hope is to come up with something commercially feasible such as "on-demand entangled photons on a chip".
     
  8. Feb 10, 2016 #7
    Hey Dr Chinese, you said the beam splitter creates path entanglement in this quote, then you contradicted yourself today by saying it doesnt. How's that?
     
  9. Feb 10, 2016 #8

    DrChinese

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    Because I keep telling you: the devil is in the details. Each context is different. You obviously have the interest. Why don't you take the time to read and understand the *entire* article? You can't make blanket statements and expect them to make sense without that understanding. Almost any such statement is easily contradicted in the complex world of Quantum Mechanics.
     
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